Am Sonntag, den 20.02.2011, 15:57 -0500 schrieb Philip Gladstone:
> I attached two C910s to a small linux box, and ran into the 'Failed to
> submit URB' problem.
>
> When I look at the descriptors for this camera, I think I understand the
> problem. I'm capturing at 5 Mpixels and I'm trying two cameras.
>
> VideoStreaming Interface Descriptor:
> bLength 38
> bDescriptorType 36
> bDescriptorSubtype 7 (FRAME_MJPEG)
> bFrameIndex 28
> bmCapabilities 0x01
> Still image supported
> wWidth 2592
> wHeight 1944
> dwMinBitRate 403107840
> dwMaxBitRate 806215680
> dwMaxVideoFrameBufferSize 10077696
> dwDefaultFrameInterval 1000000
> bFrameIntervalType 3
> dwFrameInterval( 0) 1000000
> dwFrameInterval( 1) 1333333
> dwFrameInterval( 2) 2000000
>
> The video frame size is set to 10Mb. This is surprisingly large as
> actual frames captured with MJPEG on this camera are typically 500kb or
> less. When I checked the descriptor for the uncompressed version of the
> same frame, it came back with the same value of
> dwMaxVideoFrameBufferSize (effectively 16 bits per pixel). The values
> for min/max bit rate are (correctly) calculated from the frame intervals
> and the buffer size.
>
> Typical JPEG compression gets down to 1 bit per pixel, and 2 bits is
> very unusual.
>
> What I want to know is what the impact would be of defining a new QUIRK
> that overrode the frame buffer size for compressed frames and calculated
> them at (say) 2 bits per pixel?
>
> Do other webcams get this right?
Tyke a look to the attached patch. Do you mean some thing like this?
--
Regards,
Alexey
diff --git a/drivers/media/video/uvc/uvc_driver.c b/drivers/media/video/uvc/uvc_driver.c
index a1e9dfb..e3fd466 100644
--- a/drivers/media/video/uvc/uvc_driver.c
+++ b/drivers/media/video/uvc/uvc_driver.c
@@ -465,6 +465,13 @@ static int uvc_parse_format(struct uvc_device *dev,
frame->dwMaxVideoFrameBufferSize = format->bpp
* frame->wWidth * frame->wHeight / 8;
+ /* Compressed MJPG stream is also affected. Try to recalculate
+ * FrameBufferSize to 2bpp.
+ */
+ if (format->flags & UVC_FMT_FLAG_COMPRESSED)
+ frame->dwMaxVideoFrameBufferSize = 2
+ * frame->wWidth * frame->wHeight / 8;
+
/* Some bogus devices report dwMinFrameInterval equal to
* dwMaxFrameInterval and have dwFrameIntervalStep set to
* zero. Setting all null intervals to 1 fixes the problem and
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